1. Priority Claim
This application claims the benefit of priority from European Patent Application No. 06 009468.7, filed May 8, 2006, which is incorporated by reference.
2. Technical Field
This disclosure relates to echo reduction. In particular, this disclosure relates to echo reduction and suppression of residual echo signals in communication systems.
3. Related Art
Echo reduction or suppression may be needed in communication systems, such as hands-free sets and speech recognition systems. Communication systems may include a microphone that detects a desired signal, such as a speech signal from a user. However, the microphone may also detect undesirable signals, such as echoes produced by a loudspeaker in the audio environment.
Echoes may occur when signals transmitted by a remote party and received by a near-end are output by loudspeakers at the near end. Such signals may be detected by the near-end microphone and re-transmitted back to the remote party. Echoes may be annoying to the user and may result in a communication failure.
Echo suppression may be particularly difficult if the speaker is moving, such as when a driver is using a hands-free set and also steers a vehicle. In this situation, an impulse response of the “loudspeaker-room-microphone” (LRM) environment may be time-variant. Existing echo suppression systems may be unreliable and may not be particularly effective in a time-varying LRM environment. After application of echo suppression techniques, residual echoes may be present. The severity of the residual echoes may be increased by the large delay paths associated with mobile phone services. Accordingly, a need exists for an echo reduction system capable of reducing echoes and residual echoes.